Hydrocarbon cracking catalyst and process utilizing the same

ABSTRACT

A hydrocarbon cracking catalyst comprises an ultrastable Y-type crystalline zeolite, a small pore crystalline zeolite such as mordenite, an inorganic oxide matrix and, optionally, a porous inert component. The cracking catalyst has a high activity and selectivity for the production of high octane naphtha fractions from higher boiling point hydrocarbonaceous oils. Catalytic cracking processes utilizing the catalyst are also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hydrocarbon cracking catalysts and usesthereof in catalytic cracking processes.

2. Description of the Prior Art

Hydrocarbon cracking catalysts comprising a zeolite dispersed in asiliceous matrix are known. See, for example, U.S. Pat. No. 3,140,249and U.S. Pat. No. 3,352,796.

U.S. Pat. No. 4,137,152 discloses a cracking process utilizing a mixtureof faujasite and mordenite.

U.S. Pat. No. 3,894,934 discloses catalytic cracking of hydrocarbonsutilizing a large pore zeolite and a small pore zeolite such as zeoliteZSM-5. These zeolites may be dispersed in a common matrix.

U.S. Pat. No. 3,871,993 discloses a process for upgrading the octanevalue of naphtha utilizing a shape selective catalyst such as zeoliteZSM-5, ZSM-11, ZSM-12, ZSM-21, mordenite, etc., in the absence of addedhydrogen.

U.S. Pat. No. 3,702,886 discloses use of ZSM-5 zeolite alone or incombination with other materials such as zeolites or inert materials forcatalytic cracking of hydrocarbons, see particularly columns 6 and 7.

U.S. Pat. No. 3,804,747 discloses a hydrocarbon conversion processutilizing a mixture of zeolites X and Y.

U.S. Pat. No. 3,758,403 discloses catalytic cracking comprising a largepore zeolite, such as zeolite Y, and a small pore zeolite, such asZSM-5, in a siliceous matrix. The matrix may be active or inactive, suchas silica-alumina or alumina. The use of the ZSM-5 type zeolite resultsin obtaining a fuel of increased octane number.

U.S. Pat. No. 3,769,202 discloses a combination catalyst comprising amixture of two different zeolites, one having a pore size greater than 8Angstroms and the other having a pore size of less than 7 Angstroms. Thezeolites are mixed with an inorganic oxide matrix such assilica-alumina. The catalyst is suitable for cracking and hydrocrackingof hydrocarbons.

U.S. Pat. No. 3,925,195 discloses a cracking process utilizing acatalyst comprising a mixture of rare earth hydrogen Y-type zeolite, andhydrogen or transition metal exchanged mordenite, calcium exchanged typeA zeolite, or hydrogen exchanged erionite and an amorphous matrix.

U.S. Pat. No. 3,764,520 discloses a catalyst comprising a mixture of twodifferent zeolites, one having a pore size within the range of 6 to 15Angstroms and the other having a pore size of less than 6 Angstroms incombination with an inorganic oxide support. The catalyst is useful forhydrocarbon conversion processes to give increased selectivity.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided:

(a) an ultrastable Y-type crystalline aluminosilicate zeolite havingless than about 1 weight percent rare earth metals, calculated as theelemental metal, based on the zeolite;

(b) a small pore crystalline aluminosilicate zeolite selected from thegroup consisting of erionite, mordenite, zeolite A, chabazite andoffretite, and

(c) a catalytic inorganic oxide matrix.

In one embodiment of the invention the catalyst additionally comprises aporous inorganic oxide having specific physical characteristics.

Furthermore, in accordance with the invention there is provided, acatalytic cracking process utilizing the above-stated catalyst.

DETAILED DESCRIPTION OF THE INVENTION ULTRASTABLE Y-TYPE ZEOLITECOMPONENT

"Stabilized" or ultrastable Y-type zeolites are well known. They aredescribed, for example, in U.S. Pat. Nos. 3,293,192 and 3,402,996 andthe publication, Society of Chemical Engineering (London) MonographMolecular Sieves, page 186 (1968) by C. V. McDaniel and P. K. Maher, theteachings of which are hereby incorporated by reference. In general,"ultrastable" refers to a Y-type zeolite which is highly resistant todegradation of crystallinity by high temperature and steam treatment andis characterized by a R₂ O content (wherein R is Na, K or any otheralkali metal ion) of less than 4 weight percent, preferably less than 1weight percent and a unit cell size less than 24.5 Angstroms and asilica to alumina mole ratio in the range of 3.5 to 7 or higher. Theultrastable form of Y-type zeolite is obtained primarily by asubstantial reduction of the alkali metal ions and the unit cell sizereduction. The ultrastable zeolite is identified both by the smallerunit cell and the low alkali metal content in the crystal structure.

As is generally known, the ultrastable form of the Y-type zeolite can beprepared by successively base exchanging a Y-type zeolite with anaqueous solution of an ammonium salt, such as ammonium nitrate, untilthe alkali metal content of the Y-type zeolite is reduced to less than 4weight percent. The base exchanged zeolite is then calcined at atemperature of 1000° F. to 1500° F. for up to several hours, cooled andthereafter again successively base exchanged with an aqueous solution ofan ammonium salt until the alkali metal content is reduced to less than1 weight percent, followed by washing and calcination again at atemperature of 1000° to 1500° F. to produce an ultrastable zeolite Y.The sequence of ion exchange and heat treatment results in thesubstantial reduction of the alkali metal content of the originalzeolite and results in a unit cell shrinkage which is believed to leadto the ultra high stability of the resulting Y-type zeolite. Theparticle size of the zeolites is usually in the range of 0.1 to 10microns, more particularly in the range of 0.5 to 3 microns. For use inthe present invention, the ultrastable Y-type zeolite components of thecatalyst will be substantially free of rare earth metals such as forexample cerium, lanthanum, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,yttrium, thulium, scandium, lutecium and mixtures thereof. By"substantially rare earth free" is meant that the rare earth metalcontent of the zeolite will be less than about 1 weight percent,calculated as the elemental metal, based on the zeolite. Similarly smallamounts (1 weight percent) of magnesium or calcium ions may be exchangedinto the zeolite.

Suitable amounts of the ultrastable Y-type zeolite in the catalyst ofthe present invention include from about 0.1 to about 40 weight percent,preferably from about 5 to about 25 weight percent, based on the totalcatalyst.

THE SMALL PORE ZEOLITE COMPONENT

Suitable small pore zeolite components include crystallinealuminosilicate zeolites having pore diameters not greater than about 10Angstroms, preferably not greater than 9 Angstroms. Some of thesezeolites have elliptical pore openings with a major axis of about 8 to 9Angstroms and a minor axis of about 5.5 to 7 Angstroms.

The zeolites described as being shape selective will preferentiallypermit the ingress and egress of some types of components from a mixturecomprising several types of components. The particular shape selectivezeolite that will be chosen for use in a given process will depend onthe components that it is desired to preferentially sorb into the poresof the zeolite. The small pore zeolite may be a naturally occurringzeolite or a synthetic zeolite. Suitable small pore zeolites includeerionite, chabazite, offretite, mordenite, Linde Division of UnionCarbide's zeolite designated "Zeolite A" described in U.S. Pat. No.2,822,243. The preferred small pore zeolite for use as component of thepresent catalysts is mordenite.

Mordenite is a zeolite of crystalline aluminosilicate material having asilica to alumina ratio ranging from about 9:1 up to greater than 100:1and containing elliptically shaped pores having minor and major axis ofabout 5.8 and 7.1 Angstroms, respectively. Decationizing mordeniteincreases the effective axis of the pores to about 8 Angstroms to 10Angstroms. The original cations of the small pore zeolites can bereplaced by ion exchange by methods well known in the art. Part or allof the original cations can be replaced by metal ions, ammonium ions andhydrogen ions. More preferably, the hydrogen form of mordenite isutilized as the small pore zeolite component of the catalyst of thepresent invention. Suitable weight ratio of ultrastable Y-type zeoliteto small pore zeolite ranges from about 0.5:1 to 10:1.

THE INORGANIC OXIDE GEL MATRIX

Inorganic oxide gels suitable as components of the catalyst of thepresent invention are amorphous catalytic inorganic oxides such assilica, silica-alumina, silica-zirconia, silica-magnesia, alumina-boria,alumina-titania and the like, and mixtures thereof. Preferably, theinorganic oxide gel is a silica-containing gel, more preferably theinorganic oxide gel is an amorphous silica-alumina component such as aconventional silica-alumina cracking catalyst, several types andcompositions of which are commercially available. These materials aregenerally prepared as a cogel of silica and alumina or as aluminaprecipitated on a preferred and preaged silica hydrogel. In general,silica is present as the major component in the catalytic solids presentin such gel, being present in amounts ranging from about 55 to about 100weight percent, preferably silica will be present in amounts rangingfrom about 70 to 90 weight percent. Particularly preferred are twocogels, one comprising about 75 weight percent silica and 25 weightpercent alumina and the other comprising from about 87 weight percentsilica and 13 weight percent alumina. The inorganic oxide gel componentmay suitably be present in the catalyst of the present invention inamounts ranging from about 40 to about 90 weight percent, preferablyfrom about 55 to about 75 weight percent, based on the total catalyst.

THE POROUS INERT COMPONENT

Optionally, a porous inert inorganic oxide may be used as component inthe catalyst of the present invention.

The porous inert inorganic oxide component of the catalyst of thepresent invention may be present in the finished catalyst in amountsranging from about 5 to about 35 weight percent, preferably from about10 to about 30 weight percent, based on the total catalyst. The inertporous component can be chosen from a wide variety of solid porouscatalytically inert materials. The term "catalytically inert" isintended herein to designate that the porous material has substantiallyno catalytic cracking activity or has less catalytic cracking activitythan the inorganic oxide gel component of the catalyst.

Preferably, the inert material will be a bulk material. The term "bulk"with reference to the porous material is intended herein to designate amaterial which has been preformed and placed in a physical form suchthat its surface area and pore structure is stabilized so that when itis added to an impure inorganic gel containing considerable amounts ofresidual soluble salts, the salts will not alter the surface and porecharacteristic appreciably, nor will they promote chemical attack on thepreformed inert material which could then undergo change. For example,addition of "bulk" alumina will mean a material which has been formed bysuitable chemical reaction, the slurry of hydrous alumina aged,filtered, dried, washed free of residual salts and then heated to reduceits volatile content to less than about 15 weight percent. If desired,the washed, aged hydrous alumina filter cake can be reslurried withwater and used in making the composite catalyst. The resulting inertmaterial is suitable for use as the porous inert material of the presentinvention. Suitable materials for use as inert material in the catalystof the present invention include alumina, titania, zirconia, magnesiaand mixtures thereof. Preferably, the porous material is a bulk aluminawhich may additionally be stabilized with from about 0.5 to about 6weight percent silica. Alumina stabilized with silica is commerciallyavailable. A preferred inert porous material for use as component of thecatalyst is one having initially, after heating at 1000° F. in air forsix hours, a surface area greater than about 20 square meters per gram(B.E.T. method-Brunauer, Emmett and Teller, see Van Nostrand Chemist'sDictionary 1953 edition), preferably greater than 100 m² /g, morepreferably at least 200 m² /g and a pore volume greater than about 0.25cc/g. Desirably, the inert porous material has at least 0.2 cubiccentimeters per gram pore volume in pores having diameters ranging fromabout 90 to about 200 Angstroms. These stated physical characteristicsare those of the porous inert material when taken separately aftercalcining 6 hours at 1000° F. and prior to being composited with theother components.

Alternatively and optionally, an alumina hydrosol or hydrogel or hydrousalumina slurry may be used, provided that the ultimate porous inertcomponent, when dried and calcined separately has physicalcharacteristics within the above stated ranges.

The catalysts of the present invention may be prepared by any one ofseveral methods. The preferred method of preparing one of the catalystsof the present invention, that is, a catalyst comprising silica-aluminaand, as porous inert material, alumina, is to react sodium silicate witha solution of alumina sulfate to form a silica/alumina hydrogel slurrywhich is then aged to give the desired pore properties, filtered toremove a considerable amount of the extraneous and undesired sodium andsulfate ions and then reslurried in water. Separately, a bulk aluminamay be prepared, for example, by reacting solutions of sodium aluminateand aluminum sulfate, under suitable conditions, ageing the slurry togive the desired pore properties to the alumina, filtering, drying,reslurrying in water to remove sodium and sulfate ions and drying toreduce volatile matter content to less than 15 weight percent. Thealumina is then slurried in water and blended, in proper amount, withthe slurry of impure silica/alumina hydrogel.

The zeolites are added to this blend. A sufficient amount of eachcomponent is utilized to give the desired final composition. Theresulting mixtures may be filtered to remove a portion of the remainingextraneous soluble salts therefrom. The filtered mixture is then driedto produce dried solids. The dried solids are subsequently reslurried inwater and washed substantially free of the undesired soluble salts. Thecatalyst is then dried to a residual water content of less than about 15weight percent.

The catalyst of the present invention is suitable for catalyticcracking. Catalytic cracking with the catalyst of the present inventioncan be conducted in any of the conventional catalytic cracking manners.Suitable catalytic cracking conditions include a temperature rangingfrom about 750° to about 1300° F. and at a pressure ranging from aboutatmospheric to about 100 psig, typically from about atmospheric to about20 psig. The catalytic cracking process may be carried out as a fixedbed, moving bed, ebullated bed, slurry, transferline (disperse phase) orfluidized bed operation. The catalyst of the present invention isespecially suitable for use in a fluidized bed and transferlinecatalytic cracking process. The catalyst may be regenerated atconditions which include a temperature in the range of about 1100° F. toabout 1500° F., preferably from about 1175° F. to about 1350° F.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples are presented to illustrate the presentinvention.

EXAMPLE 1

Comparative experiments were made utilizing prior art catalysts, andcatalysts of the present invention. A catalyst, herein designated"Catalyst A", is a commercially available catalyst comprising about 16%rare earth exchanged faujasite dispersed in a matrix of silica-aluminagel and kaolin. Final catalyst A comprises about 2.9 weight percent rareearth metal oxides, based on the total catalyst. The catalyst designated"Catalyst B" is not a catalyst of the present invention. Catalyst B wasmade as follows: A dilute sodium silicate solution was gelled with themeasured addition of carbon dioxide under pressure, aged and then mixedwith alum solution, the mix being brought to a pH of about 5.5. In aseparate vessel, an aqueous slurry of ball milled, oven dried bulkporous alumina was made. The alumina had a surface area (BET) of about393 m² /g, a total pore volume of 1.35 cc/g and with a pore volume of1.09 cc/g in pores ranging from about 90 to 200 Angstroms in diameter.Ball milled, calcined hydrogen form of mordenite was added and finallycalcined rare earth exchanged Y faujasite (CREY) was added. The CREYcontained 17.3 weight percent rare earth metals calculated assesquioxides. The two slurries were mixed, colloid milled and spraydried. The composite catalyst was washed free of extraneous solublesalts in a conventional manner using ammonium sulfate solution anddecationized water. The catalyst was oven dried and calcined at 1000° F.The final "Catalyst A" comprised about 16.5 weight percent hydrogenmordenite; 8.5 weight percent CREY; 20 weight percent bulk porousalumina, and 55% of a silica-alumina gel (75% silica and 25% aluminabased on the matrix gel). The final catalyst comprised 1.8 weightpercent RE₂ O₃, that is rare earth metal oxides, based on the totalcatalyst.

Catalyst C was prepared and evaluated to illustrate more directly theperformance of catalyst B with a catalyst of similar composition butwhich did not comprise a small pore zeolite. Catalyst C was made usingthe same procedure as catalyst B, that is, portions of the same impuresilica/alumina hydrogel, the same bulk porous alumina and rare earthexchanged Y-type faujasites were used, but the mordenite was excluded.Catalyst C comprises about 8.5% calcined rare earth Y faujasite, 29weight percent bulk porous alumina and 62.5 weight percentsilica-alumina gel. Chemical analysis showed catalyst C to contain 1.8weight percent RE₂ O₃, 0.16 weight percent Na₂ O, and 0.60 weightpercent SO₄. After calcination at 1000° F., catalyst C had a surfacearea of 353 m² /g and a pore volume of 0.72 cc/g.

Catalysts A, B and C were each steamed 16 hours at 1400° F. and 0 psigand evaluated for activity in a standard microactivity test. The resultsare summarized in Table I. The steamed catalysts were evaluated forcracking performance in a full cycle cracking operation. The unit was acirculating, fluidized catalytic cracking unit with a regenerator andreactor and stripper vessels. It was operated in a once through fashion,that is, there is no recycle oil mixed with fresh feed. Reactortemperature was 925° F. and regenerator temperature was 1105° F.Feedstock was a 450° to 1100° F. vacuum gas oil. The unit was operatedat a constant catalyst to oil ratio of 4. The results are summarized inTable I. In this experiment the catalysts were compared at a constant 70volume percent conversion (430° F.⁻).

                  TABLE I                                                         ______________________________________                                        Catalyst          C        B        A                                         Catalyst Activity (MAT).sup.(1)                                                                 73.9     75.0     68.0                                      ______________________________________                                        Yields and Product Qualities                                                  at 70% conversion                                                             H.sub.2 wt. %     0.053    0.031    0.027                                     C.sub.3.sup.- dry gas, wt. %                                                                    5.7      5.7      6.6                                       Total C.sub.4, vol. %                                                                           14.6     15.2     15.1                                      Butylene, vol. %  7.0      8.7      5.5                                       C.sub.5 /430° F. naphtha, vol. %                                                         60.4     61.5     59.0                                      RONC              88.9     89.0     90.3                                      MONC              79.4     79.0     80.1                                       ##STR1##         84.2     84.0     85.2                                      ______________________________________                                         .sup.(1) Microactivity test. See Oil and Gas Journal, 1966, vol. 64, page     7, 84, 85 and Nov. 22, 1971, pages 60-68.                                

The data of Table I show that catalyst B, which comprises mordenite butis not a catalyst of the present invention, was slightly more activethan catalyst C, which is a catalyst used for comparison since it has asimilar composition except for the omission of mordenite. Catalyst Balso produced less hydrogen and coke and produced more butylenes thancatalyst C. Although mordenite seems to have contributed to the crackingactivity of catalyst B, it did not produce a naphtha of higher octanenumber than catalyst C, which was the catalyst used for comparison orthe reference catalyst A.

EXAMPLE 2

A catalyst of the invention, herein designated "Catalyst D", was made ina manner similar to "Catalyst B" as follows: An aqueous slurry of ballmilled, uncalcined porous alumina having surface area and poreproperties similar to the alumina used in making catalysts B and C ofExample 1, was made and to this slurry was added first a commerciallyavailable low soda (0.12% Na₂ O) ultrastable Y-type faujasite (USY),then the desired amount of calcined, ball milled hydrogen form ofmordenite. The mixed slurry was then blended with a slurry of impuresilica-alumina hydrogel made as described in Example 1. The bulk aluminaadded to the slurry was a preformed bulk alumina stabilized with about2.5 weight percent silica which on calcination at 1000° F. had a surfacearea (BET) of 523 m² /g, a pore volume of 1.07 cc/g, a pore volume of0.21 cc/g in pores having diameter in the range of 90 to 200 Angstroms.The catalyst was spray dried to produce microspheres, washed free ofextraneous soluble salts, dried and calcined at 1000° F. The catalyst,designated "Catalyst D", which is a catalyst in accordance with thepresent invention, had a composition of about 10 weight percentultrastable Y zeolite; 10 weight percent hydrogen mordenite; 20 weightpercent bulk porous silica stabilized alumina and 60 weight percentsilica-alumina gel (said gel having a composition of 75 weight percentsilica and 25 weight percent alumina). The weights of the individualcomponents are based on the total catalyst. Chemical analysis showed Na₂O content of 0.04% and a SO₄ content of 0.57%.

EXAMPLE 3

Catalyst E is also a catalyst of reference. It was made by making amixed aqueous slurry of commercially available low soda (0.12 weightpercent Na₂ O) ultrastable Y faujasite and ball milled uncalcined bulkporous silica stabilized alumina (same alumina as the one used in makingcatalyst D) blending the slurry with a slurry of impure silica-aluminahydrogel (made as described in Example 1), spray drying the composite toform microspheres, washing the material to remove extraneous solublesalts, drying and calcining at 1000° F. Catalyst E comprised 20 weightpercent ultrastable Y-type faujasite, 20 weight percent bulk porousalumina, 60 weight percent silica-alumina gel. Chemical analysis showedan Na₂ O content of 0.08 weight percent and a sulfate content of 0.11weight percent.

Catalysts D and E were each steamed 16 hours at 1400° F. and 0 psig andevaluated for activity in a standard microactivity test. The results aresummarized in Table II. The steamed catalysts were also evaluated forcracking performance in a catalytic cracking unit previously describedin Example 1, and at the same conditions as given in Example 1. In thisset of tests, the feed used was a 560/1050° F. vacuum gas oil. Resultsof the experiments with Catalyst D are compared with the referencecatalysts, that is, catalysts "A" and "E" in the same cracking unit at aconstant 70 volume percent 430° F.⁻ conversion. The results aresummarized in Table II.

                  TABLE II                                                        ______________________________________                                        Catalyst           A        D        E                                        ______________________________________                                        Catalyst Activity (MAT)                                                                          69.      71.6     73.5                                     Product Yields and Qualities                                                  Coke, wt. %        3.5      2.5      2.7                                      H.sub.2, wt. %     0.06     0.10     0.06                                     C.sub.3.sup.- dry gas, wt. %                                                                     5.6      7.2      6.4                                      C.sub.3 H.sub.6, wt. %                                                                           3.7      4.7      4.4                                      Total C.sub.4, vol. %                                                                            13.1     13.3     11.8                                     C.sub.4 H.sub.8 (tot.), vol. %                                                                   6.8      8.0      7.6                                      C.sub.5 /430° F., vol. %                                                                  60.7     60.5     62.0                                     RON Clear          90.8     93.9     93.8                                     MON Clear          79.8     81.5     80.5                                      ##STR2##          85.3     87.7     87.2                                     C.sub.5 /430° F., incl. alkylate, vol %                                                   82.0     87.0     87.0                                     ______________________________________                                    

Catalyst D, which is a catalyst in accordance with the presentinvention, produced less coke, more light olefins, and higher naphthaoctanes than either reference catalyst A, which contained rare earthfaujasite, or reference catalyst E, which had a higher ultrastable Yzeolite content than catalyst D but no small pore zeolite (i.e.mordenite). If the increased C₃ and C₄ olefin yields are considered aspotential alkylate, the combined C₅ /430° F. cracked naphtha andalkylate naphtha yield for catalyst D is the same as for referencecatalyst E and significantly higher than for reference catalyst A. It issurprising that mordenite, when present with ultrastable Y-type zeolitein catalyst D, gave a substantially higher octane number increase thanthat obtained when combined with rare earth Y faujasite (CREY) incatalyst B (see Table I) which produced no apparent octane improvementrelative to reference catalyst C or relative to a conventional prior artcommercial catalyst A.

What is claimed is:
 1. A catalyst comprising:(a) an ultrastable Y-typecrystalline aluminosilicate zeolite having less than about 1 weightpercent rare earth metals, calculated as the elemental metal, based onthe zeolite; (b) a small pore crystalline aluminosilicate zeoliteselected from the group consisting of erionite, mordenite, zeolite A,chabazite and offretite; and (c) a catalytic inorganic oxide matrix. 2.The catalyst of claim 1 wherein said catalyst additionally comprises aporous inorganic oxide having initially a surface area greater thanabout 20 square meters per gram and a pore volume greater than about0.25 cubic centimeters per gram.
 3. The catalyst of claim 2 wherein saidporous inorganic oxide has initially a surface area greater than about100 square meters per gram and at least 0.2 cubic centimeter per gram ofits pore volume in pores having diameters ranging from 90 to 200Angstroms.
 4. The catalyst of claim 1 wherein the weight ratio of saidultrastable Y-type zeolite to said small pore zeolite ranges from about0.5:1 to about 10:1.
 5. The catalyst of claim 1 wherein said small porecrystalline zeolite is mordenite.
 6. The catalyst of claim 5 whereinsaid mordenite is the hydrogen form of mordenite.
 7. The catalyst ofclaim 2 wherein said porous inorganic oxide is selected from the groupconsisting of alumina, titania, zirconia, magnesia and mixtures thereof.8. The catalyst of claim 2 wherein said porous inorganic oxide comprisesporous alumina.
 9. The catalyst of claim 2 wherein said porous inorganicoxide comprises alumina stabilized with from about 0.5 to about 6 weightpercent silica.
 10. The catalyst of claim 1 wherein said matrixcomprises silica-alumina.
 11. The catalyst of claim 1 wherein saidcatalyst comprises from about 5 to about 40 weight percent of saidultrastable Y-type zeolite.